1. Field of the Invention
The present invention relates to a developing device, and more particularly to a developing device for forming a toner image on a photoreceptor.
2. Description of Related Art
An example of conventional developing devices is a developing device disclosed by Japanese Patent Laid-Open Publication No. 2005-17935. FIG. 10 is a skeleton framework of a developing device 500 disclosed by Japanese Patent Laid-Open Publication No. 2005-17935, and with reference to FIG. 10, the developing device 500 is described below.
In the developing device 500, a developer tank 504 is arranged adjacent to a developer support member 503. The developer tank 504 is connected with a toner tank 505 via a toner supply path 506. Further, a developer saving portion 507 and a developer separator 509 are provided. A detour 508 to the developer tank 504 is made in the developer saving portion 507. The developer separator 509 blocks a surplus part of a two-component developer 502 supported and supplied by the developer support member 503 and guides the surplus part of the two-component developer 502 to the developer tank 504 or to the developer saving portion 507 depending on the toner concentration in the developer tank 504. Moreover, a connection 513 to the toner tank 505 is formed in the developer saving portion 507. In this structure, the two-component developer 502 fed to the developer saving portion 507 can flow to the developer tank 504 and to the toner tank 505.
In the developing device 500, when the toner concentration in the developer tank 504 is low, the two-component developer 502 is temporarily guided to the developer saving portion 507, and thereby, a volume change and a flow of the two-component developer 502 are stressed. Accordingly, the developer tank 504 can take in the two-component developer with a high toner concentration from the toner tank 505 quickly. In this way, the speed of taking toner into the developer tank 504 increases, and the developing device 500 can perform continuous printing of high-density images.
In the developing device 500 disclosed by Japanese Patent laid-Open Publication No. 2005-17935, however, has a problem that the ratio by weight of toner to the developer (which will be hereinafter referred to as TC ratio) is easy to fluctuate. More specifically, in the developing device 500, the developer tank 504 and the toner tank 505 are connected to each other via the toner supply path 506 and the detour 508, and the carriers of the two-component developer 502 fed to the developer saving portion 507 move to the toner tank 505 via the detour 508. As the carriers are moving to the toner tank 505, the carriers in the developer tank 504 are decreasing, and the TC ratio in the developer tank 504 becomes higher.